You can change the default greeter by changing the configuration file to state:

/etc/lightdm/lightdm.conf

greeter-session=lightdm-yourgreeter-greeter

Enabling LightDM

Make sure to enable the lightdm daemon using systemctl so it will be started at boot.

Command line tool

LightDM offers a command line tool, dm-tool, which can be used to lock the current seat, switch sessions, etc, which is useful with 'minimalist' window managers and for testing. To see a list of available commands, execute:

LightDM can be configured by directly modifying its configuration script or by using the lightdm-set-defaults applications
that can be found in /usr/lib/lightdm/lightdm/. To see some of the options available, execute:

$ man lightdm-set-defaults

There are, however, a lot more variables to modify in the configuration file than by using the lightdm-set-defaults application.

Changing Background Images/Colors

Users wishing to have a flat color (no image) may simply set the background variable to a hex color.

Example:

background=#000000

If you want to use an image instead, see below.

GTK+ Greeter

Users wishing to customize the wallpaper on the greeter screen need to edit /etc/lightdm/lightdm-gtk-greeter.conf defining the background variable.

LightDM goes through PAM even when autologin is enabled. You must be part of the autologin group to be able to login without entering your password:

# groupadd autologin
# gpasswd -a USERNAME autologin

Note: GNOME users, and by extension any gnome-keyring user will have to set up a blank password to their keyring for it to be unlocked automatically.

Hiding system and services users

To prevent system users from showing-up in the login, install the optional dependency accountsservice, or add the user names to /etc/lightdm/users.conf under hidden-users. The first option has the advantage of not needing to updated the list when more users are added or removed.

Default Session

Troubleshooting

If you encounter consistent screen flashing and ultimately no lightdm on boot, ensure that you have defined the greeter correctly in lightdm's config file. And if you have correctly defined the GTK greeter, make sure the xsessions-directory (default: /usr/share/xsessions) exists and contains at least one .desktop file.

Power menu (restart, poweroff etc.) not available

If you have installed lightdm before lightdm-1:1.6.0-6, you might have been struck by this bug: FS#36613, to fix it run:

# chown polkitd:root /usr/share/polkit-1/rules.d

Wrong locale displayed

In case of your locale not being displayed correctly in Lightdm add your locale to /etc/environment

LANG=pt_PT.utf8

Xresources not being parsed correctly

LightDM has an upstream bug where your Xresources file will not be loaded with a pre-processor. In practical terms, this means that variables set with #define are not expanded when called later. You may see this reflected as an all-pink screen if using a custom color set with urxvt. To fix it, edit /etc/lightdm/Xsession and search for the line:

xrdb -nocpp -merge "$file"

Change it to read:

xrdb -merge "$file"

Your Xresources will now be pre-processed so that variables are correctly expanded.